HORMONES, AUXIMONES, V IT AMINES, AND TOXINS 245 



other plants. These are the so-called " auximones." For 

 example, bacterized peat seems to contain auximones which may 

 be isolated from the peat and exert a beneficial effect upon the 

 growth of various seed-plants, including common farm crops. 

 Neither the original experimental data, nor the theories which 

 have been advanced to account for the observed beneficial effects 

 of the supposed " auximones " have, as yet, sufficient confirmatory 

 evidence definitely to establish their soundness. But it seems 

 that there is a probability that some plants, at least, do elaborate 

 vitamines, or auximones, which are useful to other plants. 



TOXINS 



Toxins are substances which affect injuriously the normal 

 activities of the organism. As has been pointed out, they may be 

 the same substances which, in lesser concentrations, exert a 

 stimulating effect upon the same organism. Hence, it is 

 probably inaccurate to discuss the toxins as a distinct group of 

 substances. 



There are, however, a large number of water-soluble chemical 

 substances which are injurious to all living protoplasm, even at 

 concentrations considerably less than the point of osmotic equi- 

 librium in the juices of the protoplasm. These substances may 

 act either directly or indirectly upon the protoplasm, but at cer- 

 tain concentrations they always affect it injuriously. In the main, 

 these toxins are external agents of other than plant origin; although 

 chemical substances developed by one plant may be toxic to other 

 plants, or even to other organs of the same plant than those in 

 which they are elaborated. 



Toxins may be either general (i.e., injurious to all types of 

 plants), or specific (i.e., injurious to only certain species) in their 

 action. Examples of specific toxicity are of only minor importance 

 in plant studies. They seem to be generally explainable on the 

 basis of some unusual lack of resistance or failure of the suscep- 

 tible plants to be able to exclude the entrance of these injurious 

 substances into the protoplasm by " selective adsorption," 

 or to convert the injurious substances into insoluble and non- 

 injurious forms, as is done by other plants which are not sus- 

 ceptible to injury by these " specific " poisons. Hence, particular 

 attention need not be given to this type of toxins. 



